SEA-URCHINS AND SEA-CUCUMBERS. 301 



with microscopic life ; and though many of your captives 

 will not long survive the loss of their freedom, still 

 meanwhile you may secure many an interesting object, 

 and examine it while yet the beauty and freshness of 

 life remain. And, moreover, with care and prudence, 

 some selected subjects may be maintained in vigour, at 

 least long enough to afford you valuable information on 

 the habits, economy, metamorphosis, and development 

 of animals, of which even the scientific world knows as 

 yet next to nothing. 



I have just been so fortunate as to obtain in this way 

 one of our Sea- Urchins in its larva state ; and have it 

 now in the thin glass trough which is on the stage of the 

 microscope. It is just visible to the unassisted sight as a 

 slowly moving point in the clear water, when the vessel 

 is held up to the light ; but with the low power which I 

 am now using, it is distinctly made out in all its parts, 

 and is an object of singular elegance and beauty. 



It is, as you see, somewhat of the figure of a helmet, 

 the crest rising to a perpendicular point, which is 

 rounded, the vizor or mask descending far down, and 

 ending in two points, and a long ear hanging down on 

 each side, so as to reach the shoulders of the wearer. 

 Of course such comparisons are fanciful, but they assist 

 one in intelligible description. 



Now, the entire helmet is composed of a gelatinous 

 flesh of the most perfect transparency, so that we can 

 see with absolute clearness everything that is within it 

 And the first thing that strikes us is, that a framework 

 or skeleton of extreme delicacy, composed of glassy rods, 

 supports the whole structure. Look carefully at this, and 

 mark its symmetry and elegance. There is, then, first, a 

 rod which passes through the crest perpendicularly, and 

 carries at its lower extremity a horizontal ring. To the 

 opposite sides of this ring are soldered two other very 

 slender rods, passing down nearly in a perpendicular 



